Trauma is the leading cause of death in the US under the age of 44 with almost half of deaths attributable to acute hypovolemic circulatory collapse (AHCC). The molecular and cellular mechanisms of AHCC are not well understood and effective interventions are needed. Towards these ends, we have successfully developed reproducible models of irreversible hemorrhagic shock (HS) that leads to AHCC in rodents and established that IL-6, when added to the fluid resuscitation regimen, is capable of completely reversing AHCC and reducing mortality 5-fold. Increased Stat3 activity was observed in the hearts of IL-6-treatment animals and was accompanied by reduced cardiac apoptosis. Pharmacological targeting of Stat3 within the whole animal using a G-quartet oligodeoxynucleotide (GQ-ODN) developed by our group completely blocked both the IL-6-mediated reversal of cardiac apoptosis and the IL-6-mediated reversal of AHCC. The overall hypothesis of this proposal is that essential gene products are reduced below a critical threshold within the cardiomyocyte or endothelium of animals during irreversible hemorrhagic shock (HS) and that IL-6 acting through Stat3 maintains or increases the transcription of these genes especially those linked to mitochondrial function and cell survival. The overall goals of this proposal are: 1) to establish if Stat3 plays a role in resistance to AHCC and in its reversal by IL-6 and 2) to employ a functional genomic approach to identify genes critical for resistance to hypovolemic circulatory collapse in a comprehensive and unbiased manner. We have outlined 2 tightly focused SPECIFIC AIMS to accomplish these goals: AIM I. To establish the role of Stat3 in resistance to AHCC and in its reversal by IL-6, to establish which isoform of Stat3 is required for these effects and to identify in which cells--cardiomyocytes or endothelium--is the action of Stat3 essential. In this AIM, we will pharmacologically and genetically alter the activity of Stat3 within the heart (and endothelium, if necessary) of rats and mice and examine the effects of altered Stat3 activity on cell apoptosis and AHCC without and with IL-6 treatment. AIM II. To identify the cluster of mRNAs whose levels are maintained or increased in the vital organs of mice and rats subjected to irreversible HS by IL-6 and Stat3. We will perform Affymetrix oligonucleotide microarray analysis of RNA from the heart and lung of mice and rats to identify the list of candidate genes whose protein products may protect animals from hypovolemic circulatory collapse in the setting of irreversible HS. The long-term goals of these studies are to gain an improved molecular and cellular understanding of AHCC in the whole animal and to identify genes within essential organs that are critical for resistance to hypovolemic circulatory collapse. Identification of these genes may lead to therapeutic strategies in addition to IL-6 that induce or maintain their levels resulting in improved resuscitation outcomes in patients with serious traumatic injuries suffering from severe HS.